Digital Imaging Assists Archeologists and Provides a Glimpse into Naval History
Judith Greif, RN, MS, APNC
*Nurse Practitioner, East Brunswick, New Jersey.
Address correspondence to: Judith Greif, RN, MS, APNC, Nurse Practitioner, 50 Central Avenue, East Brunswick, NJ 08816. E-mail: grifcommedical@aol.com.
Recently on display at the Franklin Institute in Philadelphia as part of a 5-year national tour are artifacts from the wreckage of one of the world's most famous pirate ships: the Whydah Galley. The Whydah's story began in 1715 when it was built in London as a then state-of-the-art vessel designed to carry slaves from the West Coast of Africa to the Caribbean. The story ended in 1984 when it was discovered and salvaged by Barry Clifford off the coast of Cape Cod, Massachusetts. After nearly 25 years, digital technology helped archeologists and historians to recover over 200 priceless artifacts that tell the story of the first pirate ship to be discovered in North American waters, but also one that over its brief 2-year journey from slave ship to pirate ship carried individuals from many different cultures. The artifacts recovered speak to its diversity and provide a unique glimpse into the twin notorious worlds of piracy and slavery in the 1700s. The artifacts include not only treasures and the ship's bell, but day-to-day objects, such as clothing, teapots, weapons, and even human remains (a leg bone still wearing its leather shoe and silk stocking).1,2
The Whydah sailed from the Caribbean in February of 1717 after selling its human captives. It was a fast, well-equipped and well-armed ship, yet, despite this, it was captured by the pirate "Black Sam" Bellamy off the coast of the Bahamas and headed north to Maine under the leadership of pirates-not slave traders any longer. On April 26, 1717, and after only 1 prior voyage, the Whydah encountered a terrible storm, including 70 mile-per-hour winds and 30-foot swells that tossed the ship, its human cargo, and its booty from 53 captured ships, causing it to sink in Massachusetts waters, leaving all but 2 of its 146 passengers dead. The ship split in half, and its contents remained on the ocean floor until it was discovered by Clifford over 20 years ago using a map and journals created by a cartographer and ship captain named Cyprian Southhack, who had been commissioned by the colonial governor of Massachusetts to try to recover some of the loot for the British crown immediately after the tragedy (he was unsuccessful for the most part).1,2
Initially, the technology did not exist to be able to safely explore and excavate some of the hundreds of thousands of pieces of its artifact trail. Underwater exploration poses unique challenges. "Concretions" form over the years as layers of silt and organic material coat the shipwreck and its contents in thick concrete-like material (Figure 1).3 Although it preserves what is encased, it is tedious and risky to try to chip away these concretions in an attempt to discover what lies within. Digital radiography now allows archeologists to image these artifacts-some of which had been in storage in warehouses in Massachusetts for 25 years until they were scanned for National Geographic using trial and error to arrive at the correct X-ray penetration. In some cases, what was contained inside was of great interest; in other cases, archeologists were saved valuable time when it was determined that the concretions were simply solid rock.2
Details of the imaging technique were reported in the October 2007 issue of ASRT Scanner, a publication by the American Society of Radiologic Technologists. Portable imaging machines were brought on site to scan the heavy and irregularly shaped concretions, and radiologic technologists had to ascertain not only the correct dose of radiation to administer but also how to best position the scanner to view the interior, which poses a different challenge than obtaining a difficult medical X ray. Once perfected, scientists were given immediate access to digital images of the inside of these rocks, often revealing treasures not seen by the human eye for hundreds of years.2
However, the Whydah Galley is not the only fascinating shipwreck that has benefited from digital "excavation." In 2006, a high-speed scanner (computed radiography system) was donated by Fuji to the Mariners' Museum in Newport News, Virginia, to assist in the excavation and conservation of the famed Civil War battleship, the USS Monitor. It is now the nation's first National Marine Sanctuary. The Monitor was an armored turret gunboat that was sent into battle against the Confederate ship the Virginia-also an ironclad vessel. In the first battle between 2 iron warships, the Monitor was able to preserve the Union blockade of Norfolk. However, it sank in 1862 off of Cape Hatteras in a storm, was discovered in 1973, and has now been turned into a museum, in part through the use of digital imaging.4,5
Again, as with the Whydah, concretions have been analyzed, and the entire ship has been scanned. X-ray imaging allowed experts to remove concretions without damaging the artifacts they housed. In some cases, the object itself might have completely decayed; however, because of the concrete cast it left behind, the digital scanner might be able to reveal to scientists what had been present before the corrosion took place. Because the technology is digital, it also saves money by eliminating the use of film. Among the priceless artifacts discovered by conservators and archeologists from the National Oceanic and Atmospheric Administration were the skeletons of 2 crew members, coins, silverware, and pocket knives. In addition, larger artifacts of significance included the anchor, the propeller, steam engine, revolving gun turret, and guns. In total, over 1200 items were recovered-some requiring complex scanning techniques, such as when the engine and gun turrets were imaged in small sections and reconstructed into one, larger picture.5
Another famed Civil War vessel, once considered to be the "secret weapon" of the Confederacy, was its submarine, the Hunley. The Hunley was one of the earliest submarines, and it was the first to sink an enemy ship. It destroyed the USS Housatonic with a torpedo blast on February 17, 1864, but then sank along with all 9 members of its crew. Discovered in 1995, the Hunley was raised from Charleston Harbor in 2000. In order to avoid damaging the ship in the process, it was necessary to obtain precise images and measurements. This was performed through digital imaging. Two thousand measurements were obtained to determine the precise locations of important structures, such as the conning towers, the snorkel tube, the spar that housed the torpedo, the propeller, and the ballast tank. Furthermore, the Hunley was housed in a specially designed tank of temperature-controlled fresh water to preserve its contents, which were then scanned using computed radiography to identify artifacts and human remains using techniques similar to the ones used to examine the USS Monitor (Figure 2).2,6-8
In 1998, FUJIFILM NDT Systems provided the equipment for preserving and excavating an even more ancient shipwreck, the 300-year-old hull of the La Belle, which belonged to the French explorer, Rene Robert Cavelier, Sieur De La Salle, and was a gift to him from King Louis XIV. When it was discovered in the Gulf of Mexico in 1995, X rays helped to uncover more than 1 million artifacts, including medieval weaponry, jewelry, pottery, skeletal remains, and 3 cannons with the crest of Louis XIV.9
The general term for these techniques of scanning objects without destroying them is called NDT or "nondestructive testing." It has many industrial applications apart from shipwreck analysis; for example, it has also been used to image jet engines. Unlike medical imaging, NDT requires much higher doses of radiation (12 000 kV vs 150 kV). However, computed radiography helps to facilitate penetration, thus lowering the energy needed and allowing scientists to view denser materials and to view their scans more quickly and economically than if it were necessary to develop film.2
References
1. Webster D. Pirates of the Whydah. National Geographic. May 1999. Available at: http://www.nationalgeographic.com/whydah/story.html. Accessed January 26, 2009.
2. Lewis W. Medical imaging equipment uncovers sunken treasures. Encyclopedia.com. Available at: http://www.encyclopedia.com/printable.aspx?id=1G1:169458116. Accessed January 26, 2009.
3. Morris B. New artifacts brought up from pirate shipwreck. Available at: http://www.npr.org/templates/story/story.php?storyId=12589312. Accessed January 26, 2009.
4. Fuji donates digital imaging technology to assist in conservation of USS Monitor. FUJIFILM NDT Systems Web site. Available at: http://www.fujindt.com/press_uss-monitor.html. Accessed January 26, 2009.
5. High-speed scanner captures nuances of Civil War USS Monitor artifact. Available at: http://www.leica-geosystems.com/corporate/en/ndef/lgs_64189.htm. Accessed January 26, 2009.
6. H.L. Hunley Conservation Project. Digital Imaging Article Web site. Available at: http://www.thehunley.com/images/Digital%20Imaging/digitalimages.htm. Accessed January 26, 2009.
7. Fujifilm CR technology offers historical glimpse of Civil War era. FUJIFILM NDT Systems Web site. Available at: http://www.fujindt.com/news_00_11.html. Accessed January 26, 2009.
8. Haggerty R. A verified pirate ship found off Cape Cod. July 18, 2007. Available at: http://www.libertylounge.net/forums/17478-verified-pirate-ship-found-off-cape.html. Accessed January 26, 2009.
9. Uncovering historical treasures: Fuji NDT Systems donates x-ray film and processors to 300-year-old shipwreck excavation and restoration project. FUJIFILM NDT Systems. Available at: http://www.fujindt.com/news_98_3.html. Accessed January 26, 2009.
